1. Field of the Invention
The present invention relates generally to topical water-in-oil (W/O) emulsion compositions containing gellan gum which provide an enhanced rate of release of active ingredients for delivery to the skin or mucosa.
2. Background
Topical formulations generally have to combine multiple, and sometimes competing, attributes, such as those relating to aesthetics, stability, delivery and compatibility. In regard to aesthetics, topical formulations are generally required to display appropriate tactile and visual properties when applied to the skin or mucosa, while often also maintaining functionality in regard to delivery of various active ingredients onto or into the skin or mucosa.
Emulsions are widely used as topical formulations for the delivery of active ingredients, including drug and cosmetic active ingredients, to the skin or mucosa. Emulsions are generally made by preparing separate hydrophobic and hydrophilic phases and mixing the two together, usually with one or more emulsifying agents (surfactants), which reduce the surface tension between the immiscible phases creating micelles, i.e., a surfactant effect, thereby making the dispersion physically stable. The two basic types of such dispersions usually comprise 1) an oil-in-water type emulsion (O/W), which is a dispersed hydrophobic phase in a continuous aqueous phase; and 2) a water-in-oil type emulsion (W/O), which is a dispersed aqueous phase in a continuous hydrophobic phase.
The rate of release of active ingredients from a composition onto the skin or mucosa can be an important aspect of treatment. An enhanced (increased) rate of release of active ingredients can give quick relief to conditions such as infections, pruritus (itching), or pain.